Phase modulation active device, method of driving the same, and optical apparatus including the phase modulation active device

ABSTRACT

A phase modulation active device and a method of driving the phase modulation active device are provided. The phase modulation active device includes channels independently modulating a phase of incident light. The method includes selecting a first phase value and a second phase value to be used for the channels, setting a binary phase profile by allocating the selected first phase value or the selected second phase value to each of the channels quasi-periodically, in a sequence in which the channels are arranged, and driving the phase modulation active device, based on the set binary phase profile.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. patentapplication Ser. No. 15/700,391, filed Sep. 11, 2017, which claimspriority from Korean Patent Application No. 10-2016-0116580, filed onSep. 9, 2016, in the Korean Intellectual Property Office, the entirecontents of which are incorporated herein by reference.

BACKGROUND 1. Field

Apparatuses and methods consistent with example embodiments relate to aphase modulation active device, a method of driving the phase modulationactive device, and an optical apparatus including the phase modulationactive device.

2. Description of the Related Art

Optical elements that change transmission/reflection, polarization, aphase, intensity, and a path of incident light have been used in variousoptical devices. To control the above-listed characteristics of light ina desired manner in optical systems, optical modulators having variousstructures have been proposed.

For example, optically-anisotropic liquid crystals andmicroelectromechanical system (MEMS) structures using fine mechanicalmovement of light blocking/reflecting elements have been widely used inoptical modulators of the related art. Such optical modulators have along operation response time of several microseconds (μs) due to thenature of driving schemes of the optical modulators.

Attempts have recently been made to apply a meta structure to opticalmodulators. The meta structure is a structure in which a value smallerthan a wavelength of incident light is applied to a thickness, apattern, or a period. Optical modulation may be implemented in variousforms by combining phase modulation types for incident light, andvarious optical characteristics may be achieved owing to high responsespeed. Thus, the meta structure may be favorably applied to ultra-microdevices.

SUMMARY

Example embodiments may address at least the above problems and/ordisadvantages and other disadvantages not described above. Also, theexample embodiments are not required to overcome the disadvantagesdescribed above, and may not overcome any of the problems describedabove.

Example embodiments provide phase modulation active devices capable ofimplementing a desired optical performance in a combination of phasemodulation forms and methods of driving the phase modulation activedevices.

According to an aspect of an example embodiment, there is provided amethod of driving a phase modulation active device including channelsindependently modulating a phase of incident light, the method includingselecting a first phase value and a second phase value to be used forthe channels, setting a binary phase profile by allocating the selectedfirst phase value or the selected second phase value to each of thechannels quasi-periodically, in a sequence in which the channels arearranged, and driving the phase modulation active device, based on theset binary phase profile.

The setting of the binary phase profile may include repeating a processof allocating the selected first phase value to one or more firstadjacent channels among the channels, and allocating the selected secondphase value to one or more second adjacent channels among the channels,and the method may further include adjusting an optical performance ofthe phase modulation active device, based on an average value of periodsin which an arrangement pattern of the selected first phase value andthe selected second phase value is repeated.

The setting of the binary phase profile may further include setting thebinary phase profile so that the phase modulation active device steersthe incident light by θ, based on an equation,

${{\sin \theta} = \frac{\lambda}{\langle T_{k}\rangle}}.$

λ may denote a wavelength of the incident light, T_(k) may denote a kthperiod in which the arrangement pattern of the selected first phasevalue and the selected second phase is repeated, and <T_(k)> may denotethe average value of the periods.

A difference between the selected first phase value and the selectedsecond phase value may be π.

The setting of the binary phase profile may include setting a full phaseprofile having a phase value range from 0 to 2π to implement an opticalperformance of the phase modulation active device, and correcting aphase value included in the full phase profile as the selected firstphase value or the selected second phase value.

The correcting of the phase value may include, in response to the phasevalue being in first range, correcting the phase value as the selectedfirst phase value, and in response to the phase value being outsidefirst range, correcting the phase value as the selected second phasevalue.

According to an aspect of an example embodiment, there is provided aphase modulation active device including a phase modulator includingchannels configured to independently modulate a phase of incident light,a signal inputter configured to apply an input signal for phasemodulation to each of the channels, a binary setter configured to selecta first phase value and a second phase value to be used for thechannels, and set a binary phase profile by allocating the selectedfirst phase value or the selected second phase value to each of thechannels quasi-periodically, in a sequence in which the channels arearranged, and a controller configured to control the signal inputter,based on the set binary phase profile.

The binary setter may be further configured to repeat a process ofallocating the selected first phase value to one or more first adjacentchannels among the channels, and allocating the selected second phasevalue to one or more second adjacent channels among the channels, andadjust an optical performance of the phase modulation active device,based on an average value of periods in which an arrangement pattern ofthe selected first phase value and the selected second phase value isrepeated.

The binary setter may be further configured to set the binary phaseprofile so that the phase modulation active device steers the incidentlight by θ, based on an equation,

${\sin \theta} = {\frac{\lambda}{\langle T_{k}\rangle}.}$

λ may denote a wavelength of the incident light, T_(k) may denote a kthperiod in which the arrangement pattern of the selected first phasevalue and the selected second phase is repeated, and <T_(k)> may denotethe average value of the periods.

The binary setter may be further configured to set a full phase profilehaving a phase value range from 0 to 2π to implement an opticalperformance of the phase modulation active device, and correct a phasevalue included in the full phase profile as the selected first phasevalue or the selected second phase value.

The binary setter may be further configured to in response to the phasevalue being in first range, correct the phase value as the selectedfirst phase value, and in response to the phase value being outside thefirst range, correct the phase value as the selected second phase value.

A difference between the selected first phase value and the selectedsecond phase value may be π, and the first range may be π/2 to 3π/2.

The phase modulator may include an active layer having an opticalproperty changing based on an electrical signal, a nano array layeradjacent to the active layer, and including nano structures, and anelectrode layer configured to apply the electrical signal to the activelayer.

Each of the nano structures may have a shape having a dimension smallerthan a wavelength of the incident light.

The nano structures may include a metallic material.

The signal inputter may be further configured to apply a voltage betweeneach of the nano structures and the electrode layer.

The nano structures may include a dielectric material.

The phase modulation active device may further include a conductivelayer interposed between the nano array layer and the active layer, andthe signal inputter may be further configured to apply a voltage betweenthe conductive layer and the electrode layer.

According to an aspect of an example embodiment, there is provided alidar apparatus including a light source configured to emit light, and aphase modulation active device configured to steer the emitted light toan object, and including a phase modulator including channels configuredto independently modulate a phase of incident light, a signal inputterconfigured to apply an input signal for phase modulation to each of thechannels, a binary setter configured to select a first phase value and asecond phase value to be used for the channels, and set a binary phaseprofile by allocating the selected first phase value or the selectedsecond phase value to each of the channels quasi-periodically, in asequence in which the channels are arranged, and a controller configuredto control the signal inputter, based on the set binary phase profile.The lidar apparatus further includes a sensor configured to receive thelight steered to the object and reflected from the object.

The binary setter may be further configured to set binary phase profilesrespectively implementing steering angles so that the phase modulationactive device is configured to scan the object, and the controller maybe further configured to time-sequentially control the signal inputter,based on the set binary phase profiles.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of example embodiments, takenin conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram of a schematic configuration of a phasemodulation active device according to an example embodiment;

FIG. 2 is a cross-sectional view of an example of a configuration of aphase modulator that may be employed in the phase modulation activedevice of FIG. 1;

FIG. 3 is a cross-sectional view of another example of a configurationof a phase modulator that may be employed in the phase modulation activedevice of FIG. 1;

FIG. 4 is a flowchart schematically describing a method of driving aphase modulation active device, according to an example embodiment;

FIG. 5 is a diagram illustrating an example of a binary phase profileset by using the method of driving the phase modulation active device ofFIG. 4;

FIG. 6 is a flowchart for describing a detailed example of setting abinary phase profile in the flowchart of FIG. 4;

FIG. 7 is a graph of an example of correcting a full phase profile tothe binary phase profile set according to the flowchart of FIG. 6;

FIG. 8 is a graph of an example of a plurality of steering anglesimplemented according to a plurality of full phase profiles, accordingto an example embodiment;

FIG. 9 is a graph of an example of a plurality of steering anglesimplemented by setting a plurality of binary phase profiles by using amethod of driving a phase modulation active device, according to anexample embodiment;

FIG. 10 is a block diagram of a schematic configuration of a lidarapparatus according to an example embodiment; and

FIG. 11 is a diagram illustrating a beam distribution of an example ofscanning a predetermined angle range in the lidar apparatus of FIG. 10.

DETAILED DESCRIPTION

Example embodiments are described in greater detail below with referenceto the accompanying drawings.

In the following description, like drawing reference numerals are usedfor like elements, even in different drawings. The matters defined inthe description, such as detailed construction and elements, areprovided to assist in a comprehensive understanding of the exampleembodiments. However, it is apparent that the example embodiments can bepracticed without those specifically defined matters. Also, well-knownfunctions or constructions may not be described in detail because theywould obscure the description with unnecessary detail.

It will be understood that when a layer, region, or component isreferred to as being “formed on,” another layer, region, or component,it can be directly or indirectly formed on the other layer, region, orcomponent.

As used herein, the singular forms are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises” and/or “comprising”used herein specify the presence of stated features or components, butdo not preclude the presence or addition of one or more other featuresor components.

As used herein, the use of the term “the” and similar indication termscorrespond to the singular and plural forms.

Operations constituting a method may be performed in an appropriateorder, unless operations clearly indicate otherwise. The method is notlimited to the order of operations described herein. The use of any andall examples, or example language (e.g., “such as”) provided herein, isintended to better illuminate the underlying concept and does not pose alimitation on the scope of the disclosure.

In addition, the terms such as “unit,” “-er (-or),” and “module”described in the specification refer to an element for performing atleast one function or operation, and may be implemented in hardware,software, or the combination of hardware and software.

FIG. 1 is a block diagram of a schematic configuration of a phasemodulation active device 1000 according to an example embodiment. FIG. 2is a cross-sectional view of an example of a configuration of a phasemodulator 101 that may be employed in the phase modulation active device1000 of FIG. 1, and FIG. 3 is a cross-sectional view of another exampleof a configuration of a phase modulator 102 that may be employed in thephase modulation active device 1000 of FIG. 1.

The phase modulation active device 1000 may include a phase modulator100 including a plurality of channels CH_1 through CH_N that modulate aphase of an incident light, a signal inputter 200 that applies an inputsignal for phase modulation to each of the plurality of channels CH_1through CH_N, a binary setter 400 that sets a binary phase profileconfigured by using two phase values, and a controller 300 that controlsthe signal inputter 200 according to the binary phase profile.

The phase modulator 100 may include the plurality of channels CH_1through CH_N to independently modulate a phase of incident light Li. Thephase modulator 100 may include an active layer having opticalproperties that change with an applied signal and a plurality of nanostructures adjacent to the active layer. Each of the plurality of nanostructures may form the plurality of channels CH_1 through CH_N. Adetailed example of a structure of the phase modulator 100 will bedescribed with reference to FIGS. 2 and 3. Each of the plurality ofchannels CH_1 through CH_N may modulate a phase of the incident light Liaccording to a signal applied thereto from the signal inputter 200. Theinput signal from the signal inputter 200 may be determined according toa detailed structure of the phase modulator 100, e.g., materials of theactive layer and the nano structure adopted in the phase modulator 100.If the phase modulator 100 adopts a material having optical propertiesthat change with an electric signal, the signal inputter 200 may beconfigured to apply an electric signal, e.g., a voltage, to the phasemodulator 100. The incident light Li may be output as modulated light Lmin various forms by properly controlling regularity for modulating aphase in each of the plurality of channels CH_1 through CH_N of thephase modulator 100. The phase modulator 100 may perform, for example,beam steering, focusing, defocusing, beam shaping, beam splitting, orthe like, with respect to the incident light Li.

The binary setter 400 may set a phase to be modulated by each of thechannels CH_1 through CH_N to implement a target performance of thephase modulator 100. In this regard, two phase values φ1 and φ2 may beused to regulate rules that allocate the phase values φ1 and φ2 to eachof the channels CH_1 through CH_N, and thus the binary setter 400 mayset a binary phase profile to implement the target optical performance.For example, a method of arranging the two phase values φ1 and φ2 asmany times as the number of the plurality of channels CH_1 through CH_Nquasi-periodically and allocating the two phase values φ1 and φ2 in asequence in which the plurality of channels CH_1 through CH_N arearranged may be used. In this regard, when the two phase values (pi andφ2 are repeated at a predetermined period, a quasi-periodic arrangementmay include arrangements of a case in which a first period, a secondperiod, . . . , and a kth period are the same; a case in which some ofthem are the same while the others are not the same; and a case in whichall of them are different.

In an example embodiment, configurations of the phase modulator 100 andthe signal inputter 200 may be simplified by using driving according tothe binary phase profile that uses only the two phase values φ1 and φ2.The two phase values φ1 and φ2 may be determined as numerical valuesthat are easily implemented by each of the channels CH_1 through CH_N,for example, numerical values smaller than a phase limit value.

Driving using only the two phase values φ1 and φ2 may reduce intensityindicating a desired optical performance compared to a driving usingsetting of a phase value implemented by each channel of the phasemodulator 100 as various numerical values from 0° to 360°. However, inactual channel driving, although strength of an input signal increases,a phase modulation value may no longer increase due to a phase limit,and thus a process of correcting a target phase of a channel may beperformed. In the present example embodiment, two phase values amongavailable phase values that may be indicated by each of the channelsCH_1 through CH_N may be used, and an optical performance may beadjusted according to an arrangement rule of the two phase values, whichenables driving without requiring separate phase correction.

A method of setting the binary phase profile will be described in moredetail with reference to FIGS. 4 through 7.

The controller 300 may control the signal inputter 200 according to thebinary phase profile set by the binary setter 400 such that the channelsCH_1 through CH_N are independently controlled.

Referring to FIGS. 2 and 3, a detailed configuration of the phasemodulators 101 and 102 adoptable in the phase modulation active device1000 of FIG. 1 will now be described.

Referring to FIG. 2, the phase modulator 101 may include an active layer20, a nano array layer 50 in which a conductive nano structure 52 isarrayed, and an electrode layer 10 for applying a signal to the activelayer 20. The active layer 20 may include a material having opticalproperties that change with signal application. The active layer 20 mayinclude, for example, a material having a permittivity that changes withan electric field. The nano array layer 50 may include a plurality ofnano structures 52. In the drawings, one nano structure 52 forming onechannel is illustrated. An insulating layer 30 may be further disposedbetween the nano array layer 50 and the active layer 20.

The nano structure 52 may have a shape having dimensions of asub-wavelength. In this regard, the sub-wavelength means dimensionssmaller than an operation frequency of the phase modulator 101, i.e.,the incident light Li to be modulated. One dimension of the shape of thenano structure 52, e.g., any one or any combination of a thickness, awidth, and a length, may have a dimension of the sub-wavelength.

The conductive material adopted in the nano structure 52 may include ahigh-conductivity metallic material in which surface plasmon excitationmay occur. For example, at least one selected from Cu, Al, Ni, Fe, Co,Zn, Ti, ruthenium (Ru), rhodium (Rh), palladium (Pd), white gold (Pt),silver (Ag), osmium (Os), iridium (Ir), and gold (Au) may be adopted, oran alloy including any one or any combination of them may also beadopted. A two-dimensional (2D) material having superior conductivitysuch as graphene, or a conductive oxide may be used.

The active layer 20 may include a material having opticalcharacteristics that change with an external signal. The external signalmay be an electric signal. The active layer 20 may include a transparentconductive oxide (TCO) such as indium tin oxide (ITO), indium zinc oxide(IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), or the like.A transition metal nitride such as TiN, ZrN, HfN, or TaN may also beincluded in the active layer 20. An electro-optic material having aneffective permittivity that changes with application of an electricsignal, i.e., LiNbO3, LiTaO3, KTN (potassium tantalate niobate), PZT(lead zirconate titanate), etc., may also be used. Various polymermaterials having electro-optic characteristics may be used.

The electrode layer 10 may include various materials havingconductivity. The electrode layer 10 may include at least any oneselected from Cu, Al, Ni, Fe, Co, Zn, Ti, ruthenium (Ru), rhodium (Rh),palladium (Pd), white gold (Pt), silver (Ag), osmium (Os), iridium (Ir),and gold (Au). If the electrode layer 10 includes a metallic material,the electrode layer 10 may function as a reflective layer for reflectinglight as well as to apply a voltage. The electrode layer 10 may includea TCO such as ITO, IZO, AZO, GZO, or the like.

The nano structure 52 may modulate a phase of light having a wavelengthusing surface plasmon resonance occurring in a boundary between themetallic material and a dielectric material. The output phase value maybe related to a detailed shape of the nano structure 52. The outputphase value may be adjusted by a change of the optical properties of theactive layer 20 due to a voltage applied between the nano structure 52and the electrode layer 10 by a voltage source 70.

Referring to FIG. 3, the phase modulator 102 may include an active layer22, a nano array layer 60 in which a dielectric nano structure 62 isarrayed, and an electrode layer 10 for applying a signal to the activelayer 22. The active layer 22 may include a material having opticalproperties that change with signal application, for example, a materialhaving a permittivity that changes with an electric field. The nanoarray layer 60 may include a plurality of nano structures 62, and in thedrawings, one nano structure 62 forming one channel is illustrated. Aconductive layer 40 may be further disposed between the nano array layer60 and the active layer 22.

The active layer 22 may include an electro-optic material having arefractive index that changes with an effective permittivity thatchanges with application of an electric signal. As the electro-opticmaterial, LiNbO3, LiTaO3, KTN (potassium tantalate niobate), PZT (leadzirconate titanate), etc., may be used. Various polymer materials havingelectro-optic characteristics may also be used.

The electrode layer 10 may include various materials havingconductivity. The electrode layer 10 may include at least one selectedfrom Cu, Al, Ni, Fe, Co, Zn, Ti, ruthenium (Ru), rhodium (Rh), palladium(Pd), white gold (Pt), silver (Ag), osmium (Os), iridium (Ir), and gold(Au). If the electrode layer 10 includes a metallic material, theelectrode layer 10 may function as a reflective layer for reflectinglight as well as to apply a voltage. The electrode layer 10 may includea TCO such as ITO, IZO, AZO, GZO, or the like.

The nano structure 62 may have a shape having dimensions of asub-wavelength. The nano structure 62 may include a dielectric materialto modulate a phase of light having a wavelength by using Mie resonancecaused by displacement current. To this end, the nano structure 62 mayinclude a dielectric material having a refractive index higher than thatof the active layer 22, for example, a material having a refractiveindex higher than the highest value in a range in which the refractiveindex of the active layer 22 changes by application of a voltage. Thephase value output by the nano structure 62 may be related to a detailedstructure of the nano structure 62. The output phase value from the nanostructure 62 may be adjusted by a change of the optical properties ofthe active layer 10 due to a voltage applied between the conductivelayer 40 and the electrode layer 10 by a voltage source 70.

FIGS. 2 and 3 illustrate example configurations in the phase modulators101 and 102, respectively. The phase modulator 100 of the phasemodulation active device 1000 of FIG. 1 is not limited to the exampleconfigurations. Modifications of the example configurations may beadopted in the phase modulation active device 1000.

FIG. 4 is a flowchart for schematically describing a method of driving aphase modulation active device, according to an example embodiment. FIG.5 is a diagram illustrating an example of a binary phase profile set byusing the method of driving the phase modulation active device of FIG.4.

Referring to FIG. 4, the two phase values φ1 and φ2 that are to be usedas phase values in a plurality of channels included in the phasemodulation active device may be selected (operation S100). The two phasevalues φ1 and φ2 may be phase values that may be implemented by eachchannel included in the phase modulation active device and may usevalues from 0 to 2n. Taking into consideration that there may be a phaselimit, the two phase values φ1 and φ2 may be selected as numeral valuessmaller than a phase limit value of each channel. A difference |φ1−φ2|between the two phase values φ1 and φ2 may be π. For example, φ1 andφ1+π may be selected as the two phase values φ1 and φ2. The two phasevalues φ1 and φ2 may be 0 and π.

To set the binary phase profile, the selected two phase values φ1 and φ2may be arranged as many times as the channel number of the phasemodulation active device quasi-periodically and may be allocated in asequence in which a plurality of channels are arranged (operation S200).In this regard, a quasi-periodic arrangement may mean that not all theperiods at which the two phase values φ1 and φ2 are repeated are thesame.

The phase modulation active device is driven according to the set binaryphase profile (operation S300).

Referring to the binary phase profile of FIG. 5, a process of settingthe phase value φ1 with respect to one or more channels adjacent to theplurality of channels included in the phase modulation active device andsetting the phase value φ2 with respect to next adjacent one or morechannels may be repeated, and thus periods (T_(k))(k=1, 2, . . . ) atwhich an arrangement pattern of the two phase values φ1 and φ2 isrepeated may be set. A desired optical performance may be adjustedaccording to an average value <T_(k)> of the periods (T_(k)).

A numerical value of each of the periods (T_(k)) at which thearrangement pattern of the two phase values φ1 and φ2 is repeated mayhave a discrete value such as an integer multiple of a size d of achannel while the average value <T_(k)> of the periods (T_(k)) may havevarious and continuous values. Thus, the desired optical performance maybe easily adjusted through a group of differently adjusted values of theperiods (T_(k)) for each period sequence rather than setting the periods(T_(k)) as the same value, i.e., by using a method of adjusting theaverage value <T_(k)>.

A method in which the phase modulation active device implements a beamsteering angle θ in this way will now be described.

The beam steering angle θ may be implemented when a plurality ofadjacent channels indicate a linearly increasing phase. When Δφ denotesa phase difference between the adjacent channels and d denotes a channelwidth, light of a wavelength λ may be steered in a direction of theangle θ defined below.

$\begin{matrix}{{\sin \; \theta} = {\frac{\Delta\varphi}{2\pi}\frac{\lambda}{d}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the present example embodiment in which only the two phase values φ1and φ2 are used, Equation 1 above may be expressed below in which Δφdenotes a difference between the two phase values φ1 and φ2, forexample, π, and 2d denotes the average value <T_(k)> of the periods(T_(k)) at which the arrangement pattern of the two phase values φ1 andφ2 is repeated.

$\begin{matrix}{{{\sin \theta} = \frac{\lambda}{\langle T_{k}\rangle}}.} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

When the steering angle θ is adjusted according to Equation 2 above, amethod of adjusting <T_(k)> having a continuous value while using onlythe two phase values φ1 and φ2 may be used, and thus the steering angleθ may be expressed in various ways. According to the method above,scanning of a desired angle range may be easily implemented.

FIG. 6 is a flowchart describing a detailed example of setting a binaryphase profile in the flowchart of FIG. 4. FIG. 7 is a graph of anexample of correcting a full phase profile to the binary phase profileset according to the flowchart of FIG. 6.

To set the binary phase profile, the full phase profile may be set(operation S220). The full phase profile is a phase profile that whollyuses a phase value range from 0 to 2π to implement a target opticalperformance.

Phase values included in the full phase profile may be corrected as oneof the determined two phase values φ1 and φ2 (operation S250). Forexample, in a case in which the phase value φ1 appearing in the fullphase profile satisfies a first continuous range such as A≤φ≤B, a phasevalue included in the full phase profile may be corrected as the phasevalue φ1, and in other cases, the phase value may be corrected as thephase value φ2.

FIG. 7 illustrates the example in which the full phase profile iscorrected as the binary phase profile. In the graph, a rule, whichstates that A is π/2, B is 3π/2, φ1 is 0, and φ2 is π, is applied tocorrect the full phase profile as the binary phase profile. That is,when the phase value included in the full phase profile is π/2≤φ≤3π/2,the phase value may be corrected as π, and other phase values may becorrected as 0.

The rule is an example. To adjust the average value <T_(k)> of theperiods (T_(k)), other modified rules may be applied.

FIG. 8 is a graph of an example of a plurality of steering angles 8implemented according to a plurality of full phase profiles, accordingto an example embodiment.

The plurality of full phase profiles may be used to implement theplurality of steering angles 8. The graph shows that a peak value oflight intensity appears at a designed steering angle according to eachof the full phase profiles.

FIG. 9 is a graph of an example of a plurality of steering anglesimplemented by setting a plurality of binary phase profiles by using amethod of driving a phase modulation active device, according to anexample embodiment.

In the graph, unlike FIG. 8 in which full phase profiles are used, whenone binary phase profile is applied, a peak value of light intensity hasa value about half of those of the full phase profiles and appears attwo locations because the binary phase profile using two phase valueshas a symmetrical shape. That is, when a binary phase profile isdesigned to indicate the steering angle θ, an incident light may besteered at two locations of θ and −θ, and thus light intensity may behalved.

When a binary phase profile is used, although light intensity may bereduced, a size of a channel may be reduced and a driving method may besimplified as compared to when forming each channel to implement a phasechange having a range from 0 to 2π. When a predetermined scan region isscanned, a property in which a beam peak appears at two locations may beutilized to increase a scanning speed.

The method of driving the phase modulation active device described aboveis described by using a binary phase profile that performs a beamsteering function, but the inventive concept is not limited thereto.Various optical performances may be achieved by appropriately setting anarrangement pattern of two phase values. For example, the phasemodulation active device 1000 may be applied as a beam splitter thatsplits incident light in various directions, as a beam shaper thatperforms beam shaping, or as a beam steering device that steers light ina desired direction. The phase modulation active device 1000 may be usedin various optical systems using a beam splitter, a beam shaper, a beamsteering device, or the like. The phase modulation active device 1000may also actively adjust performance, e.g., steering directionadjustment, and thus the phase modulation active device 1000 may performa function such as beam scanning. The phase modulation active device1000 may be applied as a refractive optical lens capable of focusing ordefocusing, and may be applied to various optical systems using such anoptical lens. The phase modulation active device 1000 may also activelyadjust performance, and thus the phase modulation active device 1000 mayperform a function such as variable focusing.

FIG. 10 is a block diagram of a schematic configuration of a lidarapparatus 2000 according to an example embodiment.

The lidar apparatus 2000 may include a light source 1200 that irradiateslight, the phase modulation active device 1000 that steers the lightirradiated from the light source 1200 toward an object OBJ, and a sensor1400 that senses light reflected from the object OBJ.

The light source 1200 may irradiate light to be used to analyze alocation and a shape of the object OBJ. The light source 1200 mayinclude a light source that generates and irradiates light having awavelength. The light source 1200 may include a light source such as alaser diode (LD), a light-emitting diode (LED), a super luminescentdiode (SLD), or the like, which generates and irradiates light having awavelength band suitable for the analysis of the position and the shapeof the object OBJ, e.g., light having an infrared wavelength. The lightsource 1200 may generate and irradiate light in a plurality of differentwavelength bands. The light source 1200 may generate and irradiate pulselight or continuous light.

The phase modulation active device 1000 may include the phase modulator100 including the plurality of channels CH_1 through CH_N thatindependently modulate a phase of incident light, the signal inputter200 that applies an input signal for phase modulation to each of theplurality of channels CH_1 through CH_N, the binary setter 400 that setsa binary phase profile configured by using two phase values, and thecontroller 300 that controls the signal inputter 200 according to thebinary phase profile. The phase modulator 100 may have a configurationof the phase modulators 101 and 102 described above.

Between the light source 1200 and the phase modulation active device1000 and/or between the phase modulation active device 1000 and theobject OBJ, other optical members, for example, members for adjusting apath of light irradiated from the light source 1200, splitting awavelength of the irradiated light, or performing additional modulation,may be further disposed.

The binary setter 400 may set a binary phase profile that uses two phasevalues so that the phase modulation active device 1000 performs a beamsteering function. The binary setter 400 may set a plurality of binaryphase profiles that respectively implement a plurality of steeringangles so that the phase modulation active device 1000 scans the objectOBJ. The plurality of steering angles may be determined to cover a rangeof θ_(T1) to θ_(T2). As described in Equation 2 above, the binary setter400 may set the steering angles by adjusting <T_(k)> to have continuousvalues, thereby implementing a desired angle during a scanningoperation.

The controller 300 may control the signal inputter 200 to apply anappropriate input signal to the plurality of channels CH_1 through CH_Naccording to the binary phase profiles set by the binary setter 400.That is, the controller 300 may time-sequentially control the signalinputter 200 according to the set binary phase profiles.

When the phase modulation active device 1000 scans the range of θ_(T1)to θ_(T2) of the steering angles, an optical signal sensed by the sensor1400 may be used to analyze whether the object OBJ is present, alocation of the object OBJ, a shape thereof, etc.

The sensor 1400 may include an array of a plurality of sensors foroptical detection that senses light reflected from the object OBJ. Thesensor 1400 may also include arrays of sensors capable of sensing lighthaving different wavelengths.

The lidar apparatus 2000 may further include a signal processor 1600.The signal processor 1600 may perform a predetermined operation, forexample, an operation for measuring a time of flight from the opticalsignal detected by the sensor 1400, and performs three-dimensional (3D)shape identification based on the operation. The signal processor 1600may use various operation methods. For example, the signal processor1600 may use direct time measurement, wherein when pulse light isirradiated to the object OBJ, the time taken for the light to arriveafter being reflected from the object OBJ is measured by using a timer,and thus a distance is calculated based on the measured time. Acorrelation method maybe be used, wherein when the pulse light isirradiated to the object OBJ, distance is calculated based on ameasurement of brightness of the light reflected from the object OBJ.Phase delay measurement may be used, wherein when light is irradiatedhaving a continuous wave, such as a sine wave, to the object OBJ, aphase difference of the light reflected from the object OBJ is sensed,and thus the phase difference is converted into a distance. The signalprocessor 1600 may include a memory in which a program used for theoperation and other data are stored.

The signal processor 1600 may transmit an operation result, i.e.,information about the shape and location of the object OBJ, to anotherunit. For example, the information may be transmitted to a drivingcontroller or an alert system, etc., of a self-driving device employingthe lidar apparatus 2000.

The lidar apparatus 2000 may be used as a sensor for obtaining 3Dinformation about a front object in real time, and thus may beapplicable to a self-driving device, e.g., a unmanned vehicle, aself-driving vehicle, a robot, a drone, etc.

The lidar apparatus 2000 may also be applied to a black box or the likeas well as the self-driving device, to identify front or rear obstaclesat nighttime when objects are difficult to identify with an imagesensor.

FIG. 11 is a diagram illustrating a beam distribution of an example ofscanning a predetermined angle range in the lidar apparatus of FIG. 10.

Two bright lines of FIG. 11 may be scan lines. This may be a result of,as described with reference to FIG. 9 above, steering a beam in adirection of −θ by using a binary phase profile that designs thesteering angle θ. As such, when the object OBJ is scanned along one scanline, two scan lines may be formed, which may advantageously reduce atotal time taken to scan the object OBJ.

According to the method of driving the phase modulation active devicedescribed above, a binary phase profile using only two phase values maybe set, and the phase modulation active device may be driven accordingto the binary phase profile. Thus, an increase in a device area for abig phase change or a driving signal of high precision may not berequired, and a phase limit may be overcome.

The phase modulation active device described above may actively controlan optical modulation performance according to an arrangement of phasevalues of a binary phase profile and achieve a good optical modulationperformance, and thus the phase modulation active device may be suitablyapplied to various optical apparatuses.

In addition, the example embodiments may also be implemented throughcomputer-readable code and/or instructions on a medium, e.g., acomputer-readable medium, to control at least one processing element toimplement any above-described example embodiments. The medium maycorrespond to any medium or media that may serve as a storage and/orperform transmission of the computer-readable code.

The computer-readable code may be recorded and/or transferred on amedium in a variety of ways, and examples of the medium includerecording media, such as magnetic storage media (e.g., ROM, floppydisks, hard disks, etc.) and optical recording media (e.g., compact discread only memories (CD-ROMs) or digital versatile discs (DVDs)), andtransmission media such as Internet transmission media. Thus, the mediummay have a structure suitable for storing or carrying a signal orinformation, such as a device carrying a bitstream according to exampleembodiments. The medium may also be on a distributed network, so thatthe computer-readable code is stored and/or transferred on the mediumand executed in a distributed fashion. Furthermore, the processingelement may include a processor or a computer processor, and theprocessing element may be distributed and/or included in a singledevice.

It may be understood that example embodiments described herein may beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exampleembodiment may be considered as available for other similar features oraspects in other example embodiments.

While example embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

What is claimed is:
 1. A method of driving a phase modulation activedevice comprising channels independently modulating a phase of incidentlight, the method comprising: selecting a first phase value and a secondphase value to be used for the channels; setting a binary phase profileby allocating the selected first phase value or the selected secondphase value to each of the channels; and driving the phase modulationactive device, based on the set binary phase profile.
 2. The method ofclaim 1, wherein the setting of the binary phase profile comprises:repeating a process of allocating the selected first phase value to oneor more first adjacent channels among the channels, and allocating theselected second phase value to one or more second adjacent channelsamong the channels, and the method further comprises adjusting anoptical performance of the phase modulation active device, based on anaverage value of periods in which an arrangement pattern of the selectedfirst phase value and the selected second phase value is repeated. 3.The method of claim 2, wherein the setting of the binary phase profilefurther comprises setting the binary phase profile so that the phasemodulation active device steers the incident light by θ, based on anequation, ${{\sin \theta} = \frac{\lambda}{\langle T_{k}\rangle}},$wherein λ denotes a wavelength of the incident light, T_(k) denotes akth period in which the arrangement pattern of the selected first phasevalue and the selected second phase value is repeated, and <T_(k)>denotes the average value of the periods.
 4. The method of claim 1,wherein a difference between the selected first phase value and theselected second phase value is π.
 5. The method of claim 1, wherein thesetting of the binary phase profile comprises: setting a full phaseprofile having a phase value range from 0 to 2π to implement an opticalperformance of the phase modulation active device; and correcting aphase value included in the full phase profile as the selected firstphase value or the selected second phase value.
 6. The method of claim5, wherein the correcting of the phase value comprises: in response tothe phase value being in first range, correcting the phase value as theselected first phase value; and in response to the phase value beingoutside the first range, correcting the phase value as the selectedsecond phase value.
 7. A phase modulation active device comprising: aphase modulator comprising channels configured to independently modulatea phase of incident light; a signal inputter configured to apply aninput signal for phase modulation to each of the channels; a binarysetter configured to: select a first phase value and a second phasevalue to be used for the channels; and set a binary phase profile byallocating the selected first phase value or the selected second phasevalue to each of the channels; and a controller configured to controlthe signal inputter, based on the set binary phase profile.
 8. The phasemodulation active device of claim 7, wherein the binary setter isfurther configured to: repeat a process of allocating the selected firstphase value to one or more first adjacent channels among the channels,and allocating the selected second phase value to one or more secondadjacent channels among the channels; and adjust an optical performanceof the phase modulation active device, based on an average value ofperiods in which an arrangement pattern of the selected first phasevalue and the selected second phase value is repeated.
 9. The phasemodulation active device of claim 8, wherein the binary setter isfurther configured to set the binary phase profile so that the phasemodulation active device steers the incident light by θ, based on anequation, ${{\sin \theta} = \frac{\lambda}{\langle T_{k}\rangle}},$wherein λ denotes a wavelength of the incident light, T_(k) denotes akth period in which the arrangement pattern of the selected first phasevalue and the selected second phase value is repeated, and <T_(k)>denotes the average value of the periods.
 10. The phase modulationactive device of claim 7, wherein the binary setter is furtherconfigured to: set a full phase profile having a phase value range from0 to 2π to implement an optical performance of the phase modulationactive device; and correct a phase value included in the full phaseprofile as the selected first phase value or the selected second phasevalue.
 11. The phase modulation active device of claim 10, wherein thebinary setter is further configured to: in response to the phase valuebeing in first range, correct the phase value as the selected firstphase value; and in response to the phase value being outside the firstrange, correct the phase value as the selected second phase value. 12.The phase modulation active device of claim 11, wherein a differencebetween the selected first phase value and the selected second phasevalue is π, and the first range is π/2 to 3π/2.
 13. The phase modulationactive device of claim 7, wherein the phase modulator comprises: anactive layer having an optical property changing based on an electricalsignal; a nano array layer adjacent to the active layer, and comprisingnano structures; and an electrode layer configured to apply theelectrical signal to the active layer.
 14. The phase modulation activedevice of claim 13, wherein each of the nano structures has a shapehaving a dimension smaller than a wavelength of the incident light. 15.The phase modulation active device of claim 13, wherein the nanostructures comprise a metallic material.
 16. The phase modulation activedevice of claim 15, wherein the signal inputter is further configured toapply a voltage between each of the nano structures and the electrodelayer.
 17. The phase modulation active device of claim 13, wherein thenano structures comprise a dielectric material.
 18. The phase modulationactive device of claim 17, further comprising a conductive layerinterposed between the nano array layer and the active layer, whereinthe signal inputter is further configured to apply a voltage between theconductive layer and the electrode layer.
 19. A lidar apparatuscomprising: a light source configured to emit light; a phase modulationactive device configured to steer the emitted light to an object, andcomprising: a phase modulator comprising channels configured toindependently modulate a phase of incident light; a signal inputterconfigured to apply an input signal for phase modulation to each of thechannels; a binary setter configured to: select a first phase value anda second phase value to be used for the channels; and set a binary phaseprofile by allocating the selected first phase value or the selectedsecond phase value to each of the channels; and a controller configuredto control the signal inputter, based on the set binary phase profile;and a sensor configured to receive the light steered to the object andreflected from the object.
 20. The lidar apparatus of claim 19, whereinthe binary setter is further configured to set binary phase profilesrespectively implementing steering angles so that the phase modulationactive device is configured to scan the object, and the controller isfurther configured to time-sequentially control the signal inputter,based on the set binary phase profiles.